Comparing planners for rail planning in PDDL

Abstract

This paper explored the usage of the Planning Domain Definition Language in the Train Unit Shunting Problem or TUSP, an NP-hard problem that occurs in train storage. This paper focuses on the evaluation and improvement of existing planners to solve TUSP with multiple shunting yard layouts, as well as an appropriate domain with it. Starting with the implementation of multiple shunting yards in the domain, by connecting train tracks in problem instances. Followed by the evaluation of the planners, where planners are evaluated on speed, plan cost and solvability. Among the evaluated planners, the Team4 planner from the International Planning Competition 2018 demonstrates exceptional performance by successfully solving all problem instances and having the highest speed overall. Finally, the Team4 planner was optimised, specifically by improving the domain for Last In First Out, LIFO, tracks, since it encountered difficulties when solving problems that contained these tracks. The tracks were given new predicates and actions, resulting in much higher speeds for problems that consisted of LIFO tracks. Results suggest that a suitable planner has been improved for solving TUSP with multiple shunting yard layouts and that planners are indeed capable of handling the complexities that come along with multiple shunting yard layouts.